News

We aim to provide a comprehensive summary of important news in the area of constraint programming. The newsletter is published quarterly in January, April, July, and October. Please email the relevant editor with any news, event, report or profile you want published. To subscribe, please register here.

Association for Constraint Programming (ACP)

ACP EC news: April 1st, 2006 to June 30, 2006

· The ACP award for Research Excellence will be given every year. The EC devised a nomination procedure and the composition of the award committee, as follows:

·Award committee: to select among the nominees, each year the Award committee will be formed by the president and secretary of the EC, the last two award recipients, and the program chair of the CP conference where the award will be given. Members of the Award committee cannot be nominees, nor they can support a nomination by being a nominator or a reference. For year 2006, since we don't have two award recipients yet, the award committee will consist of the president, vice-president, and secretary of the EC, the 2005 award recipient, and the program chair of CP 2006.

·For the 2006 Research Award, nominations have to be sent to award06@a4cp.org by July 7, 2006. An open call for nominations was disseminated by different channels. More details can be found at http://slash.math.unipd.it/acp/call-2006.htm

·8 US$ for supporting the CSPLib. This is the cost per year of keeping the domain name (http://www.csplib.org).

* The Application Task Force was launched, lead by Barry O'Sullivan. Its role will be to find suitable means for strengthening the links between academia and industry in the CP community. An informal call for participation in the task force was disseminated by different channels.People interested in joining this task force should contact Barry O'Sullivan (b.osullivan@cs.ucc.ie).

* The next ACP EC elections will take place soon. A call for candidates will be sent to the ACP mailing list and to the Yahoo CP group in the next few weeks.

Please visit the website of the Association, http://www.a4cp.org/. It explains the purpose of the ACP and its rules, and it provides links to the AC EC elections, the Constraints Journal, the CP conferences, the CP summer school, the Yahoo! discussion group on constraints, and other activities of the ACP.

We are pleased to announce that the Twelfth International Conference on Principles and Practice of Constraint Programming (CP06: http://www.sciences.univ-nantes.fr/cp06/) will include a special workshop on "the next 10 years of constraint programming". The goal of this event will be to discuss the following questions:

-What are the achievements of the field during the last 10 years?

-What is the perception of CP by users and other research communities?

-What are the research directions for CP in 2006?

-What role can CP play within computer science research and industry?

-What are the strategic research directions likely to be in 2016?

-What application domains are of interest to us in the future?

The workshop will include a panel of invited speakers from both academia and industry, and will also leave ample time for public discussions. The content of the workshop is largely to be defined and all researchers and practitioners interested in the future of Constraint Programming are invited to share their comments and proposediscussion threads through the Yahoo! group of the Association for Constraint Programming: [2] http://groups.yahoo.com/group/constraints/

Lucas Bordeaux

Barry O'Sullivan

Pascal Van Hentenryck

CALL FOR PROPOSALS

ICLP 2007: 23rd International Conference on Logic Programming

The International Conference on Logic Programming (ICLP) is the premier conference in the field of logic programming.The Association for Logic Programming (ALP), the body that oversees ICLP and various activities related to research in Logic Programming, is seeking proposals for hosting and organizing of ICLP in 2007. Past 5 ICLPs have been held in Sitges (Spain, 2005), St. Malo (France, 2004), Mumbai (India, 2003), Copenhagen (Denmark, 2002), and Paphos (Cyprus, 2001). ICLP 2006 will be held as part of the Federated Logic Conference in Seattle, WA, USA, in August 2006.

If you are interested in organizing ICLP in 2007, please send email to Gopal Gupta, ALP Conference Coordinator, at gupta@utdallas.edu before June 20, 2007.

More information on what is involved in organizing an ICLP and guidelines on how to write a proposal for organizing an ICLP can be found in ALP's Conference Policy document that can be obtained from:

CONSTRAINTS Journal Accepted Papers

Good news for the Constraints Journal! Constraints is now covered by the Science Citation Index. The Science Citation Index, arguably the most important index for citations, "provides access to current and retrospective bibliographic information, author abstracts, and cited references found in 3,700 of the world's leading scholarly science and technical journals covering more than 100 disciplines."

CONSTRAINTS Journal Accepted Papers

The Constraints Journal publishes 4 times per year. The contents of the current issue and forthcoming papers are listed below. Links to the authors' final versions of these papers (no subscription required) and to the final published versions (subscription required) can be found here.

Career news

The Flemish research network "Declarative Methods in Informatics" is looking for applicants for postdoctoral positions. The network is supported by the FWO Research Foundation of Flanders.

The network can submit candidacies for Visiting Postdoctoral Fellowships to the FWO. Junior postdoctoral fellowships are for candidates that completed their PhD less than 5 year ago. Senior postdoctoral fellowships are for candidates that obtained a PhD between 5 years and 10 years ago. Junior fellows receive a monthly grant of 1.570 EUR; senior fellows a monthly grant of 2.070 EUR. Grants are free of taxes; social security is covered by FWO.

The fellowships are for periods from 3 to 12 months. At most three months elapse between submission of the application and the decision.

Successful candidates have a good project with a clear added value for the hosting research group and a strong publication list. If interested, get in touch with one of the contact persons.

One is regular full time (immediate opening); the other is expected to be two years duration, beginning September 2006.

Full-time position: Ph.D. or an advanced degree in computer science, or related field, and minimum five years experience in developing autonomous systems using symbolic AI techniques is required. Bachelor's degree in computer science, or equivalent, and minimum seven years experience in autonomous systems is acceptable.

Two-year position: Same requirements as above, except for years of experience: Ph.D. or advanced degree in computer science, or related field, or bachelor's degree plus three years relevant experience is required.

The following applies to both positions: Must be able to program in C/C++/Java with some familiarity in LISP and functional languages. Proven track record demonstrating software development with deployed/fielded systems, or those fielded based on the individual's efforts in real-world surroundings, is required.

Demonstrated capability in at least one or more of the following topical areas of interest in automated reasoning is desired:

+ Automated Planning/Scheduling and Execution

+ Fault Diagnosis and Recovery/Integrated Vehicle Health Mgmt (IVHM)

+ Constraint Satisfaction and/or Constraint-based Reasoning

+ Mathematical Optimization

+ Model-Based Reasoning

+ Agent Architectures

Must have excellent communication skills and be able to work well with diverse groups of people. These positions will work in an interdisciplinary environment with research and development staff as well as marine operations personnel. Must be willing to go to sea for specified periods.

- Associate Researcher position (post-doc) at Microsoft Research Cambridge

The Constraint Reasoning Group at Microsoft Research Cambridge is opening a new Associate Researcher position (post-doc). The two year position should start early 2007. We are currently collecting applications for a selective interview process which will take place late 2006 / early 2007.

Only recent PhDs in fields related to Combinatorial Optimization in general (CP, CSP, QBF, SAT/SMT) need to apply. (The PhD will have to be completed before official start.) Second level knowledge in Machine Learning and Adaptive System will also be of interest.

Within the NetWMS european project (a STREP) the constraint team (Discrete Constraints) from Nantes (http://www.emn.fr/x-info/ppc/equipe.html) is looking for a candidate for a PhD.Funding is available for 3 years (the standard duration of a PhD in France) and no teaching is required.Starting time will be september.The topic will be about geometrical constraints as described in the subject at the end of the message.

Within the European project NetWMS the goal is to design and develop a non-overlapping constraint that considers the following aspects:

(1) Handling non-rectangular shapes.

(2) Handling objects with 2,3, ..., 5 dimensions.

(3) Handling additional geometrical constraints.

The constraint and its extensions will be developped in Java and integrated within the constraint programming CHOCO (http://choco.sourceforge.net/).The project will be done by working together with INRIA and SICS.

MonashUniversity is seeking a postdoctoral research fellow to work on a newly funded research project.The problem is to combine mathematical programming and constraint programming to solve large-scale integrated scheduling problems.The project is a collaboration between the University and a Melbourne company Constraint Technologies International.

The researcher will work with colleagues at MelbourneUniversity (the MORe group), and at the Victorian NICTA laboratory in Melbourne, working on the Constraint Programming Platform project (G12).

The project is initially funded for 2 years, but constraint programming and optimisation is growing strongly at Melbourne, and subsequent longer term projects are already prepared.

The researcher will be employed as a Research Fellow Level B, and money is available to support removal costs.

Profile

CHR at Leuven.

The CHR research group works at the Department of Computer Science at the Catholic University of Leuven, Belgium. It is part of a larger group, known as DLAI -Declarative Languages and Artificial Intelligence. DLAI is headed by Maurice Bruynooghe since a long time. The activities in DLAI are roughly Analysis&Implementation, Knowledge Representation and Machine Learning. All this started by Maurice bringing Prolog from Marseille to Leuven in 1976. Our CHR work is part of Analysis&Implementation and it started four years ago when Tom Schrijvers - at that moment a PhD student with me as supervisor - was asked to do a port of the Christian Holzbaur CHR system (say the SICStus version) to hProlog (our own Prolog system that we use for experimenting with implementation). The aim at that moment was to have an evaluation of the attributed variables in hProlog, but it turned out to be the start of a lot of CHR related activity.

The CHR research group consists at this moment of five active members: Tom Schrijvers (postdoc), Jon Sneyers (second year PhD student), Leslie De Koninck and Peter Van Weert (both first year PhD students), and myself trying to keep up with their pace. Tom's initial porting resulted in a system we named the K.U.Leuven CHR system, and which has been running under SWI-Prolog (the platform we are most concerned with), XSB and hProlog for quite some time now. Recent ports have been made to Ciao Prolog, SICStus Prolog and B-Prolog. Also Yap has it running.We are constantly improving the system. Performance is very important to users and to us. Tom and Jon work on performance: an analysis framework based on abstract interpretation was developed (but it still needs exploring and tuning). Interesting (for optimization) properties of CHR programs have been identified and analyses have been designed for them. The analysis results allow the compiler to generate more efficient code. To name a few of these properties: observation, functional dependency and groundness. The analyses and optimizations are described in ICLP, PPDP, WCLP and CHR workshop papers. We are obsessed by the principle that every analysis is formally described within the refined semantics (developed by our friends in Melbourne), or an equivalent variant if it, and that optimizations are proved correct. Sometimes this seems like hair splitting, because optimizations often look obviously correct, but it is our experience that such a formal approach usually strengthens the optimization - and bugs are caught as well of course.

Jon has a keen interest in theoretical properties of CHR and his work resulted in the following strong result: minimal host-language CHR (say CHR embedded in a host language with just arithmetic and atomic equality) can implement every algorithm with the optimal space and time complexity (at the same time !).BTW, it is not just an existence proof ! We didn't stop there: our K.U.Leuven CHR system implements enough optimizations to actually achieve this optimum in practice. These results make CHR currently into the fastest executable specification language.

Leslie worked during his master thesis on a port of CLP(R) to SWI-Prolog, and on extending it to support non-linear constraints over the reals. His system is named INCLP(R): the I stands for the fact that interval extension techniques are used. The current version is available in SWI-Prolog and since it is based on rather novel techniques it outperforms older non-linear solvers easily ... even though it is written entirely in CHR (+ SWI-Prolog). One point being of course that CHR is a good language for writing such complicated algorithms in, and that our CHR implementation itself must be quite good as well :-) Non-linear solvers are not widely used currently, but they are badly needed in many application domains. Leslie's contribution shows that one doesn't need to pay a lot of money for a performant non-linear solver: it comes for free with SWI-Prolog, Leslie's recent interest is in enhancing CHR with search ... might sound weird, but there you go !

Peter implemented a Java version of CHR during his master period: the system is named the JCHR K.U.Leuven system. It is truly a wonderful marriage of CHR and Java: it offers a syntax close to the Prolog embeddings of CHR, yet it has integrated the OO ideas so that a Java developer is not scared away unnecessarily. On top of that, it is mighty efficient: CHR is compiled to Java and it beats the hell out of every other Java based CHR. In fact, JCHR will also be a serious competitor for production rule systems or business rules, once we have put in search and negation: the latter is a very interesting extension of the CHR language in which rules are not only triggered by the appearance of constraints, but also by their disappearance. Peter became recently also interested in embedding JCHR in small devices.

Tom is research wise an octopus. He is involved in every research aspect mentioned above and on top of that he has his pet interests on the side, mainly in collaboration with researchers abroad. He works on type definition reconstruction with Maurice Bruynooghe and John Gallagher in the logic programming setting, and on type inference for generalized algebraic data types with Martin Sulzmann and Peter Stuckey in the functional programming setting. Together with Gregory Duck, he prepares a book for the Springer LNCS series on the efficient implementation of CHR. He is also the principal maintainer and integrator of all our ports. Without him, there wouldn't have been a Leuven CHR team in the first place.

While we have all our private research interests and activities related to CHR, there is also a common goal: to make CHR available in a portable way across Prolog systems. It is not a flashy thing, and believe me, it takes a lot of work. But it is worth doing: I said it before ... CHR is by far the best executable specification language available right now.

As you can see, our CHR group is doing well. To a large extent, we do well thanks to our contacts with outstanding groups all over the world: Tom worked with the XSB group in Stony Brook under supervision of David S. Warren (some loose ends need tying up there). We have close collaboration with the CHR group in Ulm, Germany, headed by Thom Fruehwirth (the designer of CHR): a recent joint workshop identified a number of interesting research topics - too long to go into detail about here. We collaborate with the Melbourne/Monash teams of Peter Stuckey and Maria Garcia de la Banda: they really gave a renewed swing to the CHR field a couple of years ago by their formalization of the operational semantics of CHR. Only thanks to such a semantics, one can faithfully apply analysis, optimization and program transformation. Their refined operational semantics was dearly needed of course, but is not the end of the semantics story of course: in the mean time, every of my students has defined at least one new semantics for CHR :-) We missed the chance to collaborate more closely with Christian Holzbaur who was the first to implement CHR: unfortunately he has left the CHR scene for now.

International collaboration is very important, for us personally, and for research in general: there are so many unexplored and worthy research issues related to CHR, and we want to share them with you. If you feel you want to contribute to this wonderful area, with engineering or theoretical issues, get in touch with us and maybe we can together push CHR further in the main stream of declarative programming, and declarative programming into the main stream of computer science.

Bart Demoen

Websites:

The websites for CHR, the K.U.Leuven CHR system, JCHR and INCLP(R) can be found at

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Success stories

On June 13th 2015, the robot-lab Philae woke up on the comet 67P/Churyumov-Gerasimenko to resume a series of experiments interrupted seven months ago. These experiments were scheduled using Constraint Programming, and researchers of the team ROC of the LAAS-CNRS lab developed
propagation algorithms
to help the Scientific Operations and Navigation Centre (SONC) to efficiently achieve this task.